sonet 101

List of Terms
Stratum—Level of clock source used to categorize accuracy.
Synchronous—A network where transmission system payloads are synchronized
to a master (network) clock and traced to a reference clock.
Synchronous Transfer Module (STM)—A measure of the SDH transmission
hierarchy. STM-1 is SDH’s base-level transmission rate equal to 155 Mbps.
Higher rates of STM-4, STM-16, and STM-64 are also defined.
SPE (Synchronous Payload Envelope)—The major portion of the SONET frame
format used to transport payload and STS path overhead.
STS-1 (Synchronous Transport Signal Level 1)—The basic SONET building
block signal transmitted at 51.84 Mbps data rate.
STS-n (Synchronous Transport Signal Level n)—The signal obtained by multiplexing
integer multiples (n) of STS-1 signals together.
T1X1 Subcommittee—A committee within the ECSA that specifies SONET
optical interface rates and formats.
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VT (Virtual Tributary)—A signal designed for transport and switching of sub-
STS-1 payloads.
VT Group—A 9 row x 12 column structure (108 bytes) that carries one or more
VTs of the same size. Seven VT groups can be fitted into one STS-1 payload.
Wander—Long-term variations in a waveform.
Wideband—Services requiring 1.5-50 Mbps transport capacity.
SONET 101